Sysop chat
The BBS feature that let a caller summon the sysop and type back and forth with them in real time.
The caller picked "page sysop" from the menu and the computer in someone's bedroom started beeping. If the sysop was home and in the mood, a keypress split the screen in two, one half for each side. Every character appeared as it was typed, typos and backspaces included. On a single-line board it was the only chat there was.
Sysops could also break in uninvited, which newcomers did not always appreciate. Most software let the sysop set quiet hours for the pager, and plenty of boards ran a jokey routine that served up random excuses when nobody answered. It was an early ancestor of the customer-service chat window, with a teenager on the other end.